The present invention relates to a resin composition that can solve the various problems that occur when a multi-layer structure containing hydrolyzed ethylene-vinyl acetate copolymer is reground into a multi-layer structure, by adding the resin composition when processing. Also, the present invention relates to a process for preparing a multi-layer structure using the resin composition.
A multi-layer structure comprising, for example, polyolefin, modified polyolefin (adhesive resin) and hydrolyzed ethylene-vinyl acetate copolymer (hereinafter may be referred to as EVOH) can be reground into a multi-layer structure. However, there is the problem that degraded materials derived from EVOH develop when regrinding, by influence of the catalyst contained in polyolefin. Also, in the case that an organic or an inorganic colorant is contained in the collected multi-layer structure, there is the problem that cross-linking of EVOH occurs, due to agglomeration of the colorant.
In order to solve such problems, conventionally, a special additive that is added when regrinding has been considered and for example, JP-A-60-199040, JP-A-62-11748 and JP-A-1-178543 suggest an additive using hydrotalsite or a hydrotalsite solid solution. However, both of these additives are effective for inhibiting production of degraded materials derived from EVOH, but do not sufficiently improve the other problems. For example, when a multi-layer structure that does not contain a colorant is reground, there is the problem that transparency cannot sufficiently be maintained. In contrast, when a multi-layer structure containing a colorant is reground, further prevention of agglomeration of the colorant is required.
Also, when regrinding is conducted in this way, containers, for example, are prepared using the multi-layer structure obtained by regrinding. In such a case, EVOH in the multi-layer structure is exposed to excessive heat and there is the problem that odorous decomposition gas that is generated by thermal decomposition of EVOH tends to transfer to the inside and outside of the container. Improvement regarding this point is also desired. With respect to preventing transferring of odor, JP-A-8-104370 suggests a packaging container for cooked food in which zeolite is dispersed. However, JP-A-8-104370 describes a container in which zeolite is dispersed in a specific layer of the multi-layer structure forming the container, in order to prevent transferring of odor from the container to the food inside the container. The method of adding zeolite in any layer of the multi-layer structure, with consideration to collecting and regrinding the multi-layer structure, has not yet been suggested.